package 矩阵;

import java.util.ArrayList;
import java.util.List;

public class spiralOrder {
    public List<Integer> spiralOrder(int[][] matrix) {
        List<Integer> order = new ArrayList<Integer>();
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
            return order;
        }
        int rows = matrix.length, columns = matrix[0].length;
        int left = 0, right = columns - 1, top = 0, bottom = rows - 1;
        while (left <= right && top <= bottom) {
//            向右遍历
            for (int column=left;column<=right;++column){
                order.add(matrix[top][left]);
            }
//            向下遍历
            for (int row=top+1;row<=bottom;++row){
                order.add(matrix[row][right]);
            }

            for (int column=right-1;column>left;--column){
                order.add(matrix[bottom][column]);
            }
            for (int row=bottom;row>top;--row){
                order.add(matrix[row][left]);
            }
            left++;
            right--;
            top++;
            bottom--;
        }
        return order;

    }
}
